Grad student finds adding fresh carbon to permafrost triggers carbon loss

Permafrost
Permafrost peatbog border. Storflaket, Abisko, Sweden. Credit: Dentren/Wikipedia

Permafrost underlies nearly 85 percent of Alaska and nearly a quarter of the landmass in the northern hemisphere. This perennially frozen soil contains twice as much carbon as is found in the Earth's atmosphere. Since the Arctic is warming twice as fast as the rest of the planet, understanding carbon uptake and loss in permafrost regions is crucial to improving accuracy of climate models. It also offers clues to how this region will respond and shape a future warmer world.

As the Earth's warms and causes to thaw, that's been locked away for hundreds to thousands of years is being made available to . But what are microbes doing with that recently exposed carbon, how fast is it decomposing and how much of a difference does this make in the atmosphere?

To help answer these questions, Northern Arizona University doctoral candidate Elaine Pegoraro designed an experiment to measure how microbes respond to fresh carbon addition at different depths in collected from a field site near Healy, Alaska. Essentially, she made glucose additions to the soil three times throughout the course of a year. The results were published this month in Soil Biology and Biochemistry.

"Glucose is this really accessible energy source," said Pegoraro, who is part of the Center for Ecosystem Science and Society (Ecoss). "It's like giving the microbes a choice between brownies and a bag of frozen peas at the back of your freezer," where the frozen peas stand in for carbon found in permafrost. That carbon decomposes slowly because of biological, physical and chemical processes.

"Unless you were starving, you probably wouldn't touch the peas."

Adding glucose at the surface didn't produce much of a sustained response. But at deeper soil layers, where permafrost is found, Pegoraro and her team saw a "priming effect:" microbes respired twice as much soil carbon than the samples that didn't receive glucose. The microbes were eating the "brownies," and, in their sugar high, had the energy needed to decompose soil to access nutrients, releasing more carbon into the atmosphere.

When Pegoraro extrapolated these findings to the field, she found this priming effect accounted for 4-12 percent of carbon that is released into the atmosphere in a growing season.

"It's a considerable amount of carbon," she said.

As the Arctic warms, more plants are growing in these ecosystems, doing their part to remove some carbon from the atmosphere by incorporating it into their biomass.

But Pegoraro's findings suggest that plants may also contribute to some soil carbon loss by releasing glucose from their roots into soil.

"We need to consider priming effects to fully understand permafrost carbon dynamics," she said. "Otherwise we could underestimate how much carbon is being lost to the atmosphere."


Explore further

Tundra loses carbon with rapid permafrost thaw

More information: Elaine Pegoraro et al. Glucose addition increases the magnitude and decreases the age of soil respired carbon in a long-term permafrost incubation study, Soil Biology and Biochemistry (2018). DOI: 10.1016/j.soilbio.2018.10.009
Citation: Grad student finds adding fresh carbon to permafrost triggers carbon loss (2019, February 1) retrieved 21 September 2019 from https://phys.org/news/2019-02-grad-student-adding-fresh-carbon.html
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Feb 02, 2019
So a researcher extrapolated the effects of adding glucose at depth to permafrost.

What's the value produced in adding glucose to permafrost? If you ask me, it's like littering, but it's obviously a way to get the government to take taxpayers' money and give it to a researcher in some convoluted attempt to give the government more control over us.

I'd say let the taxpayers keep the fruits of their labor, and let the scientist try to sell their research to non-governmental organizations (e.g. corporations or individuals) for the benefit it produces. This research produces no benefit IMHO.

Feb 02, 2019
@ForFreeMinds.
So a researcher extrapolated the effects of adding glucose at depth to permafrost.

What's the value produced in adding glucose to permafrost? If you ask me, it's like littering, but it's obviously a way to get the government to take taxpayers' money and give it to a researcher in some convoluted attempt to give the government more control over us.

I'd say let the taxpayers keep the fruits of their labor, and let the scientist try to sell their research to non-governmental organizations (e.g. corporations or individuals) for the benefit it produces. This research produces no benefit IMHO.
For reasons similar in-lab experimenters do so when studying reaction/growth rates etc of beneficial and/or pathogenic bacteria/virus samples. In this case, the 'lab' was in the field, and the microbes of interest were those connected with the possible reaction to added nutrient/energy sources which Global Warming would expose/make accessible to said microbes. :)

Feb 02, 2019
As the Earth's atmosphere warms and causes permafrost to thaw, carbon that's been locked away for hundreds to thousands of years is being made available


Yes, temperature rises first, then carbon (CO2) increases afterward. Carbon does not cause the temperature increase.

Feb 03, 2019
As the Earth's atmosphere warms and causes permafrost to thaw, carbon that's been locked away for hundreds to thousands of years is being made available
Yes, temperature rises first, then carbon (CO2) increases afterward. Carbon does not cause the temperature increase.
You missed the part about man releasing huge quantities of CO2 into the atmosphere first, then rising temperatures causing events like permafrost thawing which release MORE CO2 into the atmosphere, causing more warming. See feedback loop.

Feb 03, 2019
You missed the part about man releasing huge quantities of CO2 into the atmosphere first, then rising temperatures causing events like permafrost thawing which release MORE CO2 into the atmosphere, causing more warming. See feedback loop.


That's complete BS. All the actual data clearly shows temperature rises, then CO2.
Google it, they all agree this happens, but then deny it!!! and blame man because it doesn't fit the scam theory.

Feb 03, 2019
Enacting all the green ideas will still require 80% of energy to come from oil/coal/gas. These dreamers are new age and delusional.

Sadly they'll never except safe thorium molten salt reactors developed at Oak Ridge. Yes, safe, and with no radioactive waste (so not good for making weapons grade material, why scrapped).

Feb 03, 2019
Liar deniers denying data again.

Sorry, deniers, that you hate data. It's kinda like hating the sea level rise flooding your front yard from your septic tank. Oops.

Feb 03, 2019
@Old_C_Code.
temperature rises first, then carbon (CO2) increases afterward. Carbon does not cause the temperature increase.
The Industrial Revolution beginning in late 1800s saw massive increase in wood/coal burning for subsequent centuries. The extraction/use/burning of such fossil fuels became even more widespread during World Wars I andII; and still more during the subsequent "Cold War' arms race and also the hugely expanded use of fossil coal/oil for chemicals/agriculture/steel to cater for the fast increasing populations/infrastructure needs since then. The early deforestations initially triggered warming due to less CO2 being re-sequestered by forests. Add to that initial CO2-increase trigger to the other triggers already described, and you have the MAN-INITIATED feedback...

Increased CO2--->Increased Warming--->Exacerbated increased CO2--->Exacerbated Increased Warming---> and so on.

Please rethink your starting points and logics, mate. Good luck to us all. :)

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